Various steps in the synaptic vesicle cycle are targets of a number of debilitating neurological diseases. Among these diseases are myasthenic syndromes, in which abnormal transmission at neuromuscular junctions can lead to fatigability and weakness of skeletal muscles. There is also some evidence that diseases such as schizophrenia and Alzheimer's may stem, at least in part, from impaired synaptic transmission. The long-term objective of the present research proposal is to obtain a better understanding of the temporal and spatial properties of synaptic transmission by identifying relevant molecular components and establishing how their interactions function in the synaptic vesicle cycle. Specifically, this project proposes to use the lamprey in vitro spinal cord preparation to determine the role of actin in pre-synaptic structure and function by altering actin dynamics in a living synapse. Discrete and acute pre-synaptic injections of specific actin modifying agents (phalloidin, latrunculin B, jaspamide) will be used to alter actin polymerization dynamics during rest and under physiological activation. The distribution of actin within the pre-synaptic terminal will be examined using both live imaging techniques and electron microscopy. In addition, the roles of N-WASP and the Arp2/3 complex will be examined in nerve terminal structure and function by pre-synaptically injecting antibodies and functional domains of the proteins designed to disrupt their interaction with actin and then measuring their impact on the morphology of the synapse.